The relationship between taurine and heart failure will be further explored. Taurine levels will be examined in ischemic heart tissue and a comparison between the extent of damage resulting from ischemia and taurine levels will be made. The factors contributing to taurine depletion during ischemia will be determined. In addition, a calcium paradox heart failure model will be employed to continue studying the effect of taurine on the calcium cycle. Taurine levels will also be measured in hearts which fail following exposure to conditions yielding the calcium paradox. Recently we identified two independent taurine receptors on rat heart sarcolemma. The high affinity receptor appears to be related to the beta-transport system, while the role of the low affinity receptor remains unclear. In this proposal, these receptors will be further characterized. Affinity chromatography and other standard procedures will be employed to purify the two receptors. A comparison between the properties of the purified and membrane bound receptors will be made. Of particular interest is the effect of purification on the taurine binding profile in the presence and absence of both taurine analogs and a few appropriate physiological and pharmacological effectors.